Fig.2.10 Block diagram of a generalized feedback control system

In the case of feedback control system we may input correction signals taking into account system real position regarding the established control signal. So this block diagram has 2 paths – forward and feedback and is closed. This control principle is also called closed-loop control.

We may mention many control systems using this principle.

A control system which has only feed-forward behavior responds to its control signal in a pre-defined way without responding to how the load reacts; it is in contrast with a system that also has feedback, which adjusts the output to take account of how it affects the load, and how the load itself may vary unpredictably; the load is considered to belong to the external environment of the system.